Manufacture of aromatic hydrocarbons



3,168,584 Patented Feb. 2, 1965 United States Patent Cfilice 3,168,584 MANUFACTURE OF AROMATIC HYDRO- CARBONS Maxwell Nager, Pasadena, Tex., assignor to Shell Oil Company, New York, N .Y., a corporation of Delaware No Drawing. Filed Jan. 17, 1963, Ser. No. 252,051 10 Claims. (Cl. 260--673) This application is a continuation-in-part of copending application, Serial No. 43,647, filed July 18, 1960, now US. 3,080,435, issued March 5, 1963, which is directed broadly to the iodative dehydrogenation of organic compounds by the use of oxygen and certain molten metal iodides.

This invention relates to an improved process for the production of aromatic hydrocarbons, more particularly dehydrocoupling and cyclizing of lower aliphatic hydrocarbons.

It has now been found that particular aromatic com-' pounds can be produced in high yields at moderate conversions by dehydrogenating and cyclizing simple aliphatic hydrocarbons. The present invention can, therefore, be used to manufacture aromatic compounds such as benzene, naphthalenes, xylenes, and toluene in commercial quantities using feed compositions of simple, nonaromatic hydrocarbons. The process of the present in- Vention is particularly useful in the preparation of high purity para-xylene, although it may be adapted for the preparation of various alkyl and alkenyl substituted aromatic hydrocarbons of from 7 to 30 carbon atoms.

According to the process of the present invention, C

dominantly of two or more of them and oxygen are intimately contacted with a molten alkali metal iodide to simultaneously dehydrogenate, couple, cyclize, and aromatize the simpler hydrocarbons to aromatic compounds. Thus, mixtures of two or more C to C acyclic hydrocarbons (including the dimers and trimers of such C to C hydrocarbons) or a mixture of one or more of these acyclic hydrocarbons and a product of the dehydrocoupling cycloaromatization of the hydrocarbon may be employed. Various sources of C to C hydrocarbons may be utilized, such as the dimers and trimers of C C and C hydrocarbons. These dimers and trimers may be used directly in place of the C to C hydrocarbons them selves, or may be used in monomeric form. The simple hydrocarbon feed stream may contain saturated and/or unsaturated compounds such as propane, propylene, nbutane, isobutane, butene-l, butene-2, isobutylene, isopentane, n-pentane, and isoamylenes.

Although the exact nature of the reactions involved is not completely understood, the results of studies of the effect of varying different variables, such as contact time,

relative proportion of oxygen, temperature, relative amounts of metal oxide used, etc., indicate that three ditferent reactions are involved in theprocess and are occurring together in the reaction zone: (a) reaction of oxygen with the metal iodide to form free iodine and the corresponding metal oxide and/or hydroxide; (b) reaction of the liberated free iodine with the feed hydrocarbon to form hydrogen iodide and hydrocarbon of lower H:C ratio; and (c) reaction of the hydrogen iodide with metal oxide to form metal iodide and water. Since the (b) reaction may be controlled in part by the concentration of free iodine, and this is dependent upon the proportion of oxygen and reaction (a), the extent of the (b) reaction may be controlled indirectly by varying the proportion of oxygen delivered to the molten iodide mass. The proportion of oxygen added largely determines the course and extent of the other reactions including the formation of metal oxide, the release of iodine, the dea a C or C acyclic hydrocarbons or'mixtures composed preprocess.

gree of dehydrogenation and the following formation of hydrogen iodide. It is especially important in determining the overall course of the hydrocarbon conversion since the instantaneous concentration of iodine affects the instantaneous concentrations of the various active hydrocarbon species in the reaction zone.

A number of advantages are obtained by the present Thus, whereas iodinative dehydrogenation of hydrocarbons is endothermic, and when practiced independently requires that the heat of reaction be supplied from another source, the overall heat of the reactions involved in this process is exothermic, thereby avoiding the necessity of heat transfer to the reaction zone. Moreover, since the iodinative dehydrogenation reaction alone is equilibrium limited, rapid reaction of the hydrogen iodide with the metal oxide shifts the reaction to a higher dehydrogenation conversion of the initial hydrocarbon; this is particularly valuable for the dehydrogenation of light hydrocarbons wherein the temperatures normally required for high equilibrium conversion are also conductive to thermal cracking and fragmentation. Furthermore,

the maintenance of only a very low concentration of hyan excellent heat transfer medium fortransferring the excess heat from the reaction zone. Mixtures of salts may be utilized which are either all in the molten state or wherein at least one is molten and the remainder are suspended in the molten plasma. In any case, the amount of solid or molten iodide present in the molten salt mixture is sufficient to provide, when oxidized, the necessary amount of iodine for reaction and also metallic oxide suflicient to substantially completely remove hydrogen iodide from the reaction mixture as it is formed.

The process of the present invention is based upon the discovery that the reactions involved can be controlled so as to produce aromatic hydrocarbons directly from C to C aliphatic hydrocarbons while virtually excluding the production of other, less desirable, compounds. Previously, it had beenobse'rved that the production of aromatic hydrocarbons by dehydrocoupling and cyclization of C to C hydrocarbons in a molten alkali metal iodideoxygen system was accompanied by the production of substantial amounts of poly-olefins and tar-like materials because of the random nature of the removal of hydrogen .ploying a hydrocarbon feed composed of by weight of isobutane and 25% by weight of' isobutylene, with a reactor temperature of 1060 F., and a molar ratioof oxygen to feed of from 0.5 to 1.0, 18% by weight of the reactor feed was converted to xylenes (mostly paraxylene); only 0.2% by weight of toluene was produced. By reversing the ratio of the feed reactants (25% by weight of isobutane and 75% by weight of isobutylene), but using the same reactor temperature (1060 F.),

17.6% by weight of xylenes were produced, indicating a drocarben and Water) short contact times (from 0.1 to 5.0 seconds).

that for these particular feed components (isobutane and isobutylene) the selectivity is not dependent upon the relative amounts of isobutane and isobutene in the feed.

Thus, the use of a smaller proportion of oxygen, relative to hydrocarbon, resulted in a marked increase in aromatic yield. For aromatic production, the oxygen to hydrocarbon feed ratio should be maintained for a total conversion per pass of less than 50%; a range of 30- 40% is particularly useful for aromatic xylene production. For 100% conversion of i-butane to xylene the stoichiometric oxygen requirement would be 1.25 mole oxygen per mole of i-butane. Thus, a preferred O /i-C molar ratio is from about 0.25 to about 0.5.

Similarly, p-xylene is produced from diisobutylene by heating it at temperatures of from 850 to 1050 F. using a feed ratio, moles of oxygen per moles of diisobutylene, of from 0.2 to 1.0 in a Lil molten salt system. Selectively (for the production of p-xylene) is favored by the injection of steam into the system. The steam produces LiOI-I so that a LiILiOH system is involved.

According to a preferred embodiment of the invention, p-xylene is manufactured by iodative (iodinative) dehydrogenation and coupling of isobutane. Isobutylene may be supplied as feed or produced as an intermediate in the reaction from isobutane.

Various methods of contacting the hydrocarbon feed (containing either a saturated or unsaturated hydrocarbon) with the molten metal iodide may be employed. One simple method comprises merely bubbling the hydrocarbon and oxygen in the vapor phase into the molten metal iodide (for example, lithium iodide) and recoveringthe vaporous products (principally new hy- Various types of molten salt reactors may be used as will readily occur to those skilled in the art. Reactors employing a dispersed liquid-in-gas system have been found to be particularly suitable for the process of the present invention. Reactors employing concurrent plug flow of the fluids (molten salt and vaporous reactants) with a high degree of gas-liquid contacting have been found to be especially useful. The process may be operated continuously or batchwise.

The preferred melt which is advantageously employed in the present invention is composed initially of from 75 to 99 percent by Weight of lithium iodide and from 1 to 25 percent by weight of lithium oxide and/ or lithium hydroxide. A low concentration of LiOI-I favors the production of high purity p-xylene. Anhydrous salts are used, but reagent grade lithium iodide (which contains about 29 percent by weight of water) may also be used. Excess water may be boiled ofr at about 400 C. After the process has been operated for a short period of time, the molten salt mass will contain varying amounts of other constituents. Ordinarily, it is desirable to keep such additional melt constituents to a minimum concentration (not more than about percent of the total melt by weight). The hydrocarbon and oxygen may be fed into the melt separately or may be mixed (with or without an inert gas such as nitrogen) and the mixture contacted with the melt. When a hydrocarbon-air mixture is employed, the gaseous mixture may be bubbled into the melt by introducing the mixture below the surface of the melt. The product stream is removed, condensed, and separated as desired by any suitable means.

The temperature at which the process is carried out is normally held Within the range of from 800 F. to 1100 F. 'Within this temperature range, p-xylene may be produced from ISO-C4 hydrocarbons in good yields with It has been found that the use of short contact times and temperatures of 800 F. to 1100 F. favors the production of para-xylene of from 90 to 99 mole percent purity. Contact times of from 0.1 to 3.0 seconds generally give a somewhat higher purity p-xylene (93 to 99 mole percent) than contact tirnes of from 3 to 8 seconds at reactor temperatures of more than 1100 F. By contact time is meant the average residence time of the hydrocarbon reactant e.g., butane, isobutane, propane, propylene, isobutylene, diisobutylene or isoamylene in contact with the molten salt in the reaction zone. In general, the purity of the p-xylene produced is improved by decreasing the residence time of the iso-C; or iso-C (indicating an unsaturated hydrocarbon such as isobutylene) in the molten salt reaction zone and/ or by decreasing the temperature. These conditions were also unexpectedly found to result in an increase in the conversion of the iso-C s for a given i-C /O ratio. The improvement in purity is believed to be due to minimizing purely thermal conversion while increase in conversion is attributable in large part to improved gas-liquid contacting at the higher gas velocities used to obtain shorter residence times. Some xylene may be produced thermally (without the interaction with iodine or the Lil salt) and the mole ratio of the para-xylene to the meta-xylene produced by this reaction (P/M) is only in the order of from 1.5 to 2. The purity of the final p-xylene product can be increased by conducting the reaction so as to avoid this thermal reaction.

The important of controlling the relative amount of the thermal reaction is apparent from a comparison of the results of Examples 3 and 4 given in Table I which is a summary of several runs using an isobutylene feed. For the same mole ratio of oxygen to feed and with the same residence time, significantly higher conversion is obtained at the higher temperature. However, this increase in conversion (from 33.1% to 40.8%) is accompanied by a decrease in p-xylene purity; this decrease is a measure of the nonselective thermal formation of xylene. Only small amounts of normal butane and butenes (up to about 1.0% by Weight) were in the feed initially, and only small amounts of these compounds are formed by isobutylene isomerization in the molten salt reaction zone.

TABLE I Para-xylene from isobutylene-bafiled react0r2% w. LiOH/98% Lil Example No 1 2 3 4 5 6 Reactor Temperature, F. 900 925 950 1,000 1,050 950 Residence time, sec- 2. 5 1. 1. 4 1. 0 1. 5 Oz/iOi. mole ratio 0.38 0. 41 0 42 0.42 1 0.42 HzO/Oz, mole ratio 2 2 2 2 2 Para-xylene purity, percent m 94. 7 95. 3 94. 5 94. 0 90. 8 95. 6 Conversion, percent w 36. 5 32. 5 33. 1 40. 8 42. 8 33. 1 Selectivity, percent w:

CH4 0. 2 0.4 0. 5 1.1 0.7 0. 4 02114" 1.1 1.8 1.3 1.2 1.1 1.0 07119.. 0. 2 0.3 0.4 0.3 0. 2 .0. 2 O5H 2.1 2. 4 2. 7 3. 7 1. 7 2. 5 C4Hu-. 0.8 0. 7 1. 0 0.6 0.4 0. 5 IC-IIIlO. 0. 4 4. 1 0. 4 0. 9 1. 1 2. 5 1C Hg 0. 1 0. 2 0. 1 0. 2 0.1 Benzene 1. 3 1. 8 0.8 0. 5 0. 4 0. 5 Toluene. 1. 9 1. 7 1. 8 0. 9 2. 4 1. 3 Xylenes. 68. 8 71.0 69. 3 69. 4 78. 2 69. 2 DM 2 0.4 1.2 2.0 2.4 0.5 0.4 Naphtha1ene+CuH5I 0. 6 0. 4 0. 6 0. 6 0. 4 0. 7 Methyhiaphthalene C H7I 0.6 0.1 0.4 0.3 0.3 0.3 2.7-dimethylnaphthalene- 5. 5 2. 6 3. 5 4. 0 3. 6 5. 0 Oil 0. 2 0.1 0.1 0.1 0. 1 0.1

CO; 7.2 4.7 6.3 6.2 4.6 6.6 Oxygen balance, percent m 106 91 93 116 106 93 1 Oxygen used in this run. In all other runs in Table I air was used. 2 Dimethallyl (2,5-dimethyl-1.5hexadiene).

Other factors also are to be considered in relation to the selectivity of the process for the production of p-xylene. For example, the substitution of oxygen for air (still maintaining the same oxygen/feed molar ratio) in the oxidation zone seems to have only a slight, if any, affect on the ratio of p-xylene to m-xylene in the product stream (see Examples 3 and.4 of Table I). In-

5 creasing the oxygen/feed molar ratio within limits already discussed also causes a small increase in the p- Xylene purity. In the commercial preparation of very pure p-xylene these factors become increasingly important.

Table II illustrates the conversion of diisobutylene to para-xylene using temperatures of from 875 C. to 1000 Fiand moleratios (oxygen/feed) of from 0.5 to 0.95.

TABLE II Conversion of diisobutylene to p-xylene Example No 7 8 9 Temperature, F 1, 000 875 875 O /Feed, mole ratio. 0.5 0.95 0. 5 Steam input, cc./min 84 Yields, percent w.,no loss bases:

a r 1. 2 0. 2 0.2 C1-C 2. 9 0. 1 0. 1 C4 25. 7 4. 6 5.0 C5-C1- 12. 7

r 31.6 80.0 70.3 Toluene- 0. 5 1. 2 Xylenes 2 23. 9 9. l 20. 4 Carbon (from C an a 1.3 0.4 0.3 Carbon (tarry residue) ND 5. 6 2. 5 Measured recovery, percent w 96. 6 100. 8 102. 7 Iodine in product, percent w. 4. 5 3. 6 3. 4

Conversion, percent In 68. 4 20.0 29. 7 Selectivity, percent 111 34. 9 45. 5 68.9 Average reactor contact time (sec.) 1. 5 1.0 1. 5

1 Largely isobutylene.

2 Largely p-xylene.

3 Not determined.

4 Not corrected for iodides in product.

Table III summarizes the results obtained when isobutylene and mixtures of isobutane and isobutylene were reacted in a molten salt reactor containing about 90 to 95 percent by weight of U1 and from 5 to 10 percent by weight of LiOH (added directly to the molten reactor mass or formed in situ by the injection of steam). Temperatures employed were varied from 1000 F. to 1100 F.

TABLEIII Conversion of zsobutylene and zsobutane to p-xylene Example N0 10 11 12 13 Feed Iso- Iso- 25% ISO-C4] 75% Iso-Gr/ C4- C4 75% Iso-Cr 25% Iso-Cr Temperature, F 1, 100 1, 020 1,060 1, 060 Oz/Feed, mole... 0.5 0.5 0.625 0.875 Yields, percent w., no

loss basis:

0.9 1. 1 3. 7 3.2 0. 8 1. O 1. 2 1. 4 6S. 4 72. 7 69. 5 72. 9 2.0 1. 2 3. 9 l. 1 0.3 0.2 0. 1 0. 2 0.4 0.2 0.3 0.2 Xylenes 1 23. 4 19. 8 17. 6 18.0

Carbon (from C0 and CO2) 3. 8 3. 8 3. 7 3.0 Iodine in Product,

percent w 1. 2 1. 6 1; 2 1.3 Total Recovery, Percent w 96.3 96. 4 97. 4 99. 2 Gonversionfl percent 111.- 29. 6 26. 1 26. 5 26. 0 Selectivity? percent in... 83. 5 80. 2 71. 8 73.8 Average reactor contact 1.0

time (sec) 1. 4 1. 5 1. 2

1 Basis total 04 charged and not corrected for iodides in product.

Included amongthe identified side products in the reaction product obtainedfrom the dehydrocoupling of iso-butene are 2,5-dimethyl-1,5-hexadicne, 1,1,3-trimethylcyclopentane, benzene, toluene, naphthalene, Z-methylnaphthalene, 2,7-dimethyln-aphthalene, trans-p-methylstilbene, trans-p-p-dimethylstilbene, methylphenanthrene, 3,-dimethylphenanthrene, 2 methyl-7-(trans-p-mcthylstyryl)-naphtha1ene, iodomethane, vinyl iodide, 2-iodopropene, Z-methyl-l-iodopropene, iodobenzene, piodotoluene, and iodomethylnaphthalene. From the wide variety of possible products, it is clear that the selectivity achieved for the production of pxylene is quite unexpected. The process of the present invention produces p-xylene of very high purity in spite of the wide variety of side products. By employing a different feed, it is possible to tailor the process for the production. of other specific aromatic compounds. (See Table TV.) For example, using a propylene feed and temperatures above 600 C. with a lithium iodidelithium hydroxide melt (or initially even with lithium iodide alone), benzene is the major product.

TABLE IV Reaction studiescoupling Example No 14 15 16 17 Feed Hydrocarbons Iso- 50-Iso- 50-Propane, 75-Propybutylene butane, 50-Isolene 50-n-Butane butylcne 25-Tolnene O IHC, mole ratio 0. 3 0.8 1.0 0.3 Reactor temperature, F 975 980 1,000 1,030 Conversion, percent I11 23 1 40 2 74 3 21 Selectivity, percent 0.5 1. 2 0. 9 1.1 2.1 0.9 0. 6 0. 2 0. 5 1.3 26. 7 O. 3 5. 2 26. 8 0 4 O. 9 7. 6 1. 4 44. 9 0. 9 O. 1 1. 2 0. 2 1. 4 3. 7 1. 1 l0. 7 33. O Tolueueuu 7. 4 O. 6 28. 8 C3 aromatics. 5.0 6. 0 17. 5 4. 3 C9 aromatics. 0.2 Napthalene 0. 8 33. 6 2-methylnaphtl'ialene 1.8 2,7-dimethylnaphtl1alene a 17. 9 l. 4 1. 4 trans-Stilbcnc 2. 8 1. 8 2. 4 1. l 0.6 3. 7 5.0 5 14. 2

tribution, percent in:

Ethylbeuzene 17. 7 2. 5 p-Xylenc. 91. 0 32. O 95. 4 l3. 8 m-Xylcne 8. 9 40. 2 4. 5 oXylene. 0. 1 10. 1 0. 1 Styrene .1 S3. 7

' lgl pmbincd conversion of i-Cl" and 11-04": Conversion ratio, iCf/nC C ombined conversion of 03 and 104: Coni ersion ratio, Ca/iC4 C0 n1bined conversion of Ca" and toluene: Conversion ratio, Ca/ Toluene 3.

4 Believed to contain 3,6-dimethylphenanthrene and trans-P-P'- dimcthylstilbene.

5 Includes heavy ends.

Even more complex aromatic compounds may be produced in significant yields under proper reaction conditions: Another example of the production of such a compound is the preparation of 2,7-dimethylnaphthalene (18 mole percent selectivity) from isobutylene using a molar feed ratio (oxygen/isobutylene) of about 0.3 with a molten Lil-LiOH system at a temperature of about 975 F. (see Table IV).

When isooutane or isobutylene is fed to a molten salt reactor according to the present invention, a whole series of coupled products may be obtained by proper control of the dehydrogenation coupling rate. The results indicate that the coupling probably takes place via the methallyl free radical. For example, para-xylene produced in the process reacts with iso-butylene orisobutane to produce dimethylnaphthalene (C H The dimethylnaphthalene reacts with another mole of isobutylene or isobutane to produce dimethylphenanthrene (0 F1 in preference to 2,6-dimethylanthracene, and repetition of the process two more times produces (3 1-1 and C H hydrocarbons, respectively, but in smaller quantities. The successive reactions can be represented by the following equations in which the ring-hydrogens have been omitted as customary for simplification:

Para- In a similar fashion, isobutylene and m-xylene co-react, probably through the intermediates methallyl and mmethlbenzyl free radicals, to produce corresponding dimethyl-naphthalenes. Thus, when an equimolar mixture of isobutylene and m-xylene was iodatively dehydrogenated under conditions as set out in Table V by passing the feed components through a horizontal pipe containing molten LiI/LiOH and baffied with bafile plates to insure intimate mixing of the feed components and the molten mass followed by gas-liquid separation, the dimethylnaphthalene fraction separated from the product stream contained equivalent amounts of 1,7- and 2,6-dimethylnaphthalenes, showing that ring closure of the coupled occurs at the same rate at the two available positions. Other results given in Table V show that isobutylene was also converted in high yield to p-xylene and that a large proportion of the converted m-xylene produced meta, meta'-dimethylstilbene, which was predominately the trans-isomer. Toluene similarly gives rise to stilbene (see Table IV) and p-xylene gives rise to p,p-dimethylstilbene.

TABLE V Coupling reactions-m-xylene and isobutylene melt. 95-98% Wt. Lil, 25% wt. LiOH Reactorhorizontal baflled-pipe:

Temperature, F 1000 8 TABLE VContinued iC H 1.3 Benzene 1.4 Toluene 2.0 p-Xylene 23.2 2-methyl-4- (meta-tolyl) -butene-1 2.0 06 and fi-methylnaphthalene 1.3 1,7-dimethylnaphthalene 12.2 2,6-dimethylnaphthalene 12.2 2,7-dimethylnaphthalene 0.1 Cis-meta, meta'-dimethylstilbene 2.7 C16H18 2 Trans-meta, eta'-dimethylstibene 17.2 Nonvolatile residue 1.3 CO 6.0 CO 2.7

Total conversion-conversion ratio isobutylene/m-xylene 2 11151 is probably a mixture of metaand para-substituted ditolyl ethanes.

Further details of the examples are as follows:

EXAMPLES 1-6 Isobutylene was fed ma molten salt composition containing 2% LiOH and 98% LiI (percentages by weight). Reaction conditions and product distribution are summarized in Table I.

EXAMPLES 79 A LiILiOH melt was prepared by mixing LiI.3H O and LiOH.H O in correct proportions to give 95 LiI-5% LiOH in the hot anhydrous melt. Table II tabulates the results obtained by dehydrocyclizing diisobutylene to para- Xylene under varying temperatures and with different molar feed ratios (oxygen/ hydrocarbon feed).

EXAMPLES 10-13 A molten mixture of 95% LiI and 510% LiOH was employed as reaction and contacting medium and iodine supply and hydrogen iodide acceptor. The feed compositions, reaction conditions, and product distributions are given in Table III.- The feed compositions were as follows:

Example 10Isobutylene. Example 11-Isobutylene. Example 12--A mixture of 25% isobutane and 75% isobutylene (molar). Example 13A mixture of 75 isobutane and 25% isobutylene (molar).

EXAMPLES 14-17 Using a LiILiOH melt composition (98% by weight LiI and 2% by weight of LiOH) and an average residence time in the reactor of from 1 to 4 seconds, the following feed hydrocarbons were sent to the reactor:

Example 14Isobutylene.

Example 15-50% isobutane and 50% n-butane (molar).

Example 1650% propane and 50% isobutylene (molar).

Example 17-75% propylene and 25 toluene (molar).

Results, showing the distributions of the aromatic compounds formed, conversions, selectivities, oxygen/hydrocarbon molar feed ratios, and reactor temperatures are summarized in Table IV. The symbol i-C in Table IV indicates isobutane (a saturated C hydrocarbon). Similarly, the symbol iC represents isobutylene. The other abbreviations used are self-explanatory.

EXAMPLES 18-28 The reactor (which may be a riser type or a simple stirred pot apparatus) was charged with 141 grams of reagent grade lithium iodide which contained about 29 percent water. Most of the water was boiled off at temperatures of up to 400 C., and then 14 grams of lithium hydroxide was added. The mixture was then heated to the reaction temperature (400 C. to 650 C.) and nitrogen was bubbled through the melt until the reactants were charged. The reactor was heated by an electric furnace.

Air and the organic compound were introduced below the surface of the melt through a common inleta Provision was made for withdrawing gaseous spot samples immediately following the receiver for analysis by gas-liquid chromatography during the run. Table V1 is a summary of eleven runs using a propylene/ oxygen mole ratio of 8.

TABLE VI Molar Mole ratio of Us Example Reactor Temp, percent of equivalent 1 No. type O- propylene converted Benzene Biailyl Ethene Riser 550 23 1 1. 1

(10...- 590 1 1.3 1. do. 640 16 1 O. 5 1. 410...- 500 24 l 1.75 1. (lo 514/554 14 1 2.0 1. clo 500 14 1 2. 5 04 ..do.. 450 G 1 3.5 .0. do 400 8 Stirred 450/495 i 1 1 0. pet. 27 3 do 460 -2 2S do.. 405 -2 1 3 1 C3 equivalent=moles of benzene (or biallyl) in product X2 or moles of ethene X36.

. 2 lodopropene is the major product. 3 Melt composed of lithium iodide alone.

4 Benzene is the major product.

Table Vll shows that temperatures above 400* C. favor conversions and higher proportions of benzene. in the I riser reactor, the hydrocarbon and oxygen feed mixture Was fed into the lower end of an upright elongated tubular'vessel which opened at its lower end into a body of molten lithium iodide-lithium hydroxide disposed in a larger tubular vessel surrounding the riser tube and displaced from the upper open end of the riser tube. The velocity ofthe feed mixture was contrfolledxto disperse a portion of the molten mass in it and carry it withthe gaseous mixture out the top of the riser tube. The dissuch as 0.25 and 0.5 in the riser operation give higher persedrnelt was separated by gravity-from the gaseous materials and returned to the body of molten material at the lower endof the riser tube.

I claim as my invention: Y

1. A processfor the selective conversion of c to C acyclic hydrocarbons"represented by the formula C I-l to C H2 +2 to .aproduct containing a major percentage of aromatic hydrocarbon which comprises intimately contacting said acyclic hydrocarbon at a temperature offrom I about 800 :F.-1100 F. for 0.1t0 Sseconds with an iodide and a minor proportion of. alkali'metal base, while intimately contacting the rnolten salt with an amount of oxygen to give from about 10% to 50% conversion of the hydrocarbon, the molar ratio of said oxygen to said acyclic hydrocarbon being from about 0.25 to about 0.5. a 1

-2. A process in accordance with claim 1, wherein the alkali metal iodide is lithium iodide and the alkali metal base is lithium hydroxide.

3. A process for the preparation of a product containing amajor percentage of para-xylene which Comprises intimately contacting (3 1-1 to C H hydrocarbon at a temperature of about 800-1100 P. for 0.1 to 5 seconds his process in accordance with claim 3, wherein the hydrocarbon feed is essentially isobutane.

'5. A process in accordance withclaim 3 whereinthe hydrocarbon feed is essentially isobutylene.

6. A process for the preparation of dimethyl naphthalene which comprises intimately contacting an equimolar mixture of a (l -hydrocarbon having a ratio of hydrogen to carbon of at least 2 andat least 1 xylene isomer, at a temperature of about 800-1100 F. for 0.1 to 5 seconds with an essentially homogeneous molten salt composition consisting essentially of amajor proportion of lithium iodide and a minor proportion of lithium hydroxide, while intimately contacting the molten salt with an amount of;

oxygen to give from about 10% to about 50% conversion of the hydrocarbon, the molar ratio of said oxygen to said mixture being from about 0.25 to about 0.5.

7. A process in accordance with claim 6, wherein the C hydrocarbon is isobutylene and the xylene isomer is paraxylene, and the dimethyl naphthalene is 2,7-dimethylnaphthalene.

8. A process in accordance with claim 6, wherein the C hydrocarbon is isobutane and the xylene'isomer is para-xylene.

9. Aprocess in accordance with claim 6, wherein the i the xylene isomer is i C hydrocarbon is isobutylene and meta-xylene.

' 10. A process in accordance with claimo, wherein the C hydrocarbon is isobutane' and the xylene isomer is meta xylene.

References (Cited in the file of this patent UNITED STATES PATENTS 3,030,435 3/63 Nager gee-674.5- 3,].06 520 l0/63 'Bittner V Cloth-673.5

793,214 4/58 Great Britain.

ALPHONSO n. SULLIVAN, Primary E m-51a, J

FOREIGNPATENTS" 1- I {I a 

1. A PROCESS FOR THE SELECTIVE CONVERSION OF C3 TO C5 ACYCLIC HYDROCARBONS REPRESENTED BY THE FORMULA CNH2N TO CNH2N+2 TO A PRODUCT CONTAINING A MAJOR PERCENTAGE OF AROMATIC HYDROCARBON WHICH COMPRISES INTIMATELY CONTACTING SAID ACYCLIC HYDROCARBON AT A TEMPERATURE OF FROM ABOUT 800*F.-1100*F. FOR 0.1 TO 5 SECONDS WITH AN ESSENTIALLY HOMOGENEOUS MOLTEN SALT COMPOSITION CONSISTING ESSENTIALLY OF A SUBSTANTIAL PROPORTION OF ALKALI METAL IODIDE AND A MINOR PROPORTION OF ALKALI METAL BASE, WHILE INTIMATELY CONTACTING THE MOLTEN SALT WITH AN AMOUNT OF OXYGEN TO GIVE FROM ABOUT 10% TO 50% CONVERSION OF THE HYDROCARBON, THE MOLAR RATIO OF SAID OXYGEN TO SAID ACYCLIC HYDROCARBON BEING FROM ABOUT 0.25 TO ABOUT 0.5.
 3. A PROCESS FOR THE PREPARATION OF A PRODUCT CONTAINING A MAJOR PERCENTAGE OF PARA-XYLENE WHICH COMPRISES INTIMATELY CONTACTING C4H8 TO C4H10 HYDROCARBON AT A TEMPERATURE OF ABOUT 800*-1100*F. FOR 0.1 TO 5 SECONDS WITH AN ESSENTIALLY HOMOGENEOUS MOLTEN SALT COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF LITHIUM IODIDE AND A MINOR PROPORTION OF LITHIUM HYDROXIDE, WHILE INTIMATELY CONTACTING THE MOLTEN SALT WITH AN AMOUNT OF OXYGEN TO GIVE FROM 30% TO 40% CONVERSION OF THE HYDROCARBON THE MOLAR RATIO OF SAID OXYGEN TO SAID HYDROCARBON BEING FROM ABOUT 0.25 TO ABOUT 0.5.
 6. A PROCESS FOR THE PREPARATION OF DIMETHYL NAPHTHALENE WHICH COMPRISES INTIMATELY CONTACTING AN EQUIMOLAR MIXTURE OF A C4-HYDROCARBON HAVING A RATIO OF HYDROGEN TO CARBON OF AT LEAST 2 AND AT LEAST 1 XYLENE ISOMER, AT A TEMPERATURE OF ABOUT 800*-1100*F. FOR 0.1 TO 5 SECONDS WITH AN ESSENTIALLY HOMOGENEOUS MOLTEN SALT COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF LITHIUM IODIDE AND A MINOR PROPORTION OF LITHIUM HYDROXIDE, WHILE INTIMATELY CONTACTING THE MOLTEN SALT WITH AN AMOUNT OF OXYGEN TO GIVE FROM ABOUT 10% TO ABOUT 50% CONVERSION OF THE HYDROCARBON, THE MOLAR RATIO OF SAID OXYGEN TO SAID MIXTURE BEING FROM ABOUT 0.25 TO ABOUT 0.5. 